Mechanical filter with coupling wires



United States Patent C) MECHANICAL FILTER WITH COUPLING WIRES Lloyd M.. Ibsen, North Hollywood, Calif., assignor to Collins Radio Company, Cedar Rapids, Iowa, a corporation of Iowa Application August 16, 1955, Serial No. 528,757

4 Claims. (Cl. S33-71) This invention relates in general to electromechanical filters, and in particular to a filter which has variable coupling between the discs so as to eliminate spurious response.

Various patents have issued on electromechanical filters which operate on the principle of converting electrical energy to mechanical energy, filtering the energy to pass desired frequencies, and then converting the mechanical energy back to electrical energy. For example, Patents Nos. 2,693,579 and 2,693,580 illustrate mechanical filters wherein a plurality of discs are connected by coupling wires and driven by the driving wire.. The present invention relates to an electromechanical filter wherein the coupling wires do not extend across all the discs. This substantially eliminates spurious responses that would otherwise exist.

A feature of this invention isto provide a structure which is relatively free from spurious response.

Further objects, features, and advantages of this invention will become apparent from the following description and claims when read in view of the drawings, in which:

Figure 1 is a top view with the cover removed of an electromechanical filter according to this invention;

Figure 2 is a side sectional view taken on lines 2-2 from Figure 1; and

Figure 3 is a schematic view of the mechanical filter of this invention.

Figure 1 illustrates a base plate 10 to which are attached a pair of stand-offs 11 and 12. The stand-offs comprise two portions 13 and 14 respectively, and 15 and 16 respectively, which are connected together by suitable set screws 17 and 18. The stand-offs hold cylinders 21 and 22. A first disc 23 is attached to the end of the cylinder 21 as by welding. A second supporting disc 24 is connected to the cylinder 22. The discs 23 and 24 are formed with central openings 26 and 27 respectively, for a purpose to be later described. A first plurality of resonating discs, which by way of example are shown as three, and .are numbered 28, 29, and 30, are supported from the first disc 23 by means of a plurality of longitudinal coupling wires 31. For example, there might be three coupling wires 31 equally spaced about the discs 28, 29, and 30.

A second plurality of active discs 32, 33, and 34, which might for example be three, are supported from the supporting disc 24 by means of coupling wires 36 which are attached to their peripheries and to the peripheries of the disc 24. A driving wire 37 passes through the discs 23, 28, 29, 30, 32, 33, 34, and 24. It is rigidly connected to the active discs 28-30 and 32-34. A driving wire 37 passes through the openings 26 and 27 formed in the supporting discs 23 and 24. The ends of the driving wire 37 extend within the confines of the cyliners 21 and 22.

A coil form 38 is mounted within the cylinder 21 and coil form 39 is mounted within the cylinder 22. A Winding 41 is wound about coil form 38 and winding 42 2,829,350 Patented Apr. l, 1958 ICC In operation an input signal is supplied to the terminals A 46 and 47 and energizes the driving coil 41. If the input has frequency components within the pass band of the filter it will pass through the filter. The coil 41 drives the driving wire 37 due to magnetostriction. The rst group of coupling wires 31 causes the discs 28, 29 and 30 to resonate as a unit. The driving wire 37 couples energy to the disc 32 which drives the discs 33 and 34, which also resonate as a unit. The discontinuity caused by the termination of the coupling wires 31 and 36 will eliminate spurious responses which would otherwise exist. The output signal induced in the winding 42 is caused by magnetostrictive motion of the end of wire 37. This output is supplied to the terminals 51 and 52.

The discs and coupling and driving wires may be made of a suitable nickel alloy, as for example Ni Span C, which material exhibits the magnetostrictive property and which has a very desirable temperature coefiicient so that the frequency of the structure does not vary with ternperature changes.

Although the invention has been described with respect to a particular embodiment thereof, it is not to be so limited as changes and modifications may be made therein which are within the full intended scope of the invention as defined by the appended claims.

I claim:

1. An electrochemical filter comprising a base plate, a`

pair of stand-offs mounted on said base plate, a pair of cylinders supported respectively in spaced alignment by said stand-offs, a first supporting disc attached to the end of the first cylinder, a second supporting disc attached to the end of the second `cylinder in spaced-parallel alignment with said first disc, said supporting discs being mounted on adjacent ends of said cylinders, a first plurality of coupling wires extending from the periphery of the first supporting disc toward the second supporting disc and terminating between them, a first plurality of active resonators with their peripheries attached to the first plurality of coupling wires and mounted in a parallel-spaced relationship, a second plurality of coupling wires attached to the periphery of the second supporting disc and extending toward the first supporting disc and terminating between said discs, a second plurality of resonating discs with their peripheries attached to the second supporting disc and mounted in parallel-spaced relationship, the first and second supporting discs formed with central openings, a driving magnetostrictive wire extending through the openings in said first and second supporting discs and attached to the plurality of resonating discs at their center, the driving wire extending within the first cylinder, a driving coil mounted in the first cylinder, and an output coilsecond supporting disc and terminating between them, a first plurality of active resonating discs with their peripheries attached to the first plurality of. coupling wires and mounted in a parallel-spaced relationship, a second plurality of coupling wires attached to the periphery of the second supporting disc and extending toward the first supporting disc and terminating between said discs, a second plurality of resonating discs with their periphexies attached to the second plurality of coupling wires and mounted in parallel-spaced relationship, the first and second supporting discs formed with central openings, a magnetostrictive driving wire extending through the openings in said first and second supporting discs and attached to the first and second pluralities of resonating discs at their center, the driving wire extending within the rst cylinder, a driving coil mounted in the first cylinder, an output coil mounted in theV second cylinder and the driving wire extending therethrough, a first biasing magnet attached to the first stand-ofi above the first cylinder, and a second biasing magnet attached to the second stand-off above the second cylinder.

3. Aresonator assembly for electrochemical filters cornprising a pair of cylinders supported in spaced-axial alignment from a base plate, a first supporting disc attached to the inner end of said first cylinder, a first plurality of coupling wires attached to the periphery of said supporting disc and extending cantileverally therefrom, a first plurality of resonating discs mounted in parallelspaced relationship with their peripher-ies attached to the first plurality of coupling Wires, an opening formed through said first supporting disc, a second supporting disc attached to the inner end of said second cylinder and formed with a central opening, a second plurality of coupling wires extending from the periphery of said second suppoiting disc, `a second plurality of active resonating discs with their peripheries attached to the second plurality of coupling Wires and mounted in a parallel-spaced relationship, a magnetostrictive driving wire extending through the openings formed in the first and second supporting discs and extending through and attached to the centers of the first and second pluralities of active resonating discs.

4. An apparatus according to claim 3 wherein said active resonating discs are resonant at substantially the same frequency.

References Cited in the le` of this patent UNITED STATES PATENTS 2,617,882 Roberts Nov. 11, 1952 2,693,580 Peterson Nov. 2, 1954 2,716,887 Smith Sept; 6, 1955 

